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args <- commandArgs(TRUE)
options(digits=22)
library("Matrix")
library("matrixStats")

X <- as.matrix(readMM(paste(args[1], "X.mtx", sep="")))
colVariances <- t(colVars(X))

# R outputs the variance of a single number as NA, whereas a more
# appropriate value would be 0, so replace all NAs with zeros.
# This is useful in the case of colVars of a row vector.
colVariances[is.na(colVariances)] <- 0

writeMM(as(colVariances, "CsparseMatrix"), paste(args[2], "colVariances", sep=""));
